In cases of performing medicinal solutions mixing operations in hospitals, such as preparing infusion medicinal solutions, it has been well known that a plurality of medicinal solutions filled respectively in medicine bottles called vials are aspirated by means of a syringe and are mixed in this syringe to prepare the infusion medicinal solutions. The medicinal solutions thus prepared are then discharged from the syringe so as to be filled into an infusion bag or the like.
In such medicinal solution mixing operations performed in hospitals, there are cases where a large amount of a medicinal solution of high viscosity, such as dextrose in water in high concentration, is dispensed using a syringe of a large content of about 50 ml, for example. In these cases, quite a large force of more than one hundred N is needed for driving the syringe by pushing and pulling a plunger. The medicinal solutions to be prepared may include one that is carcinogenic and harmful to healthy people, such as a carcinostatic agent, which needs to be handled with extreme care. Accordingly, it is quite a workload for an operator to handle a syringe in order to mix medicinal solutions.
There has been proposed, as a device assisting in operating a syringe, a syringe drive device that is used for injecting a medicinal solution into a human body at a constant quantity, for example. A syringe drive device of this type generally includes a fixing section that holds a flange of an outer tube of a syringe to fix the syringe, and a holder that holds a brim section of a plunger so as to axially move the plunger with respect to the syringe fixed to the fixing section. Further, a pressure detector provided at the holder detects an internal pressure of the syringe in accordance with a force for axially moving the plunger, so as to indicate a signal corresponding to the detected internal pressure to an operator (refer to JP 1998-192402 A).
FIG. 14 is a view showing a configuration of a conventional syringe drive device disclosed in JP 1998-192402 A. In this syringe drive device, rotation of a motor is converted to linear motion of a holder 1, and a plunger receiver 4 of the holder 1 pushes a brim section 3 of a plunger 2, so that a medicinal solution in a syringe 5 is discharged. A holder arm 6 presses the brim section 3 of the plunger 2 against the plunger receiver 4. There is further provided a pressure sensor 7 between the plunger receiver 4 and the holder 1 with a pressure transmission portion 8 being interposed therebetween. By indicating a signal corresponding to a detection value of the pressure sensor 7 in the case where the brim section 3 is pressed, an alert is issued indicating blockage in a route of an infusion solution or disengagement of the syringe. More specifically, an alert is issued indicating blockage when the detected pressure is too large. On the other hand, an alert is issued indicating disengagement of the syringe when the detected pressure is too small. This configuration allows an operator to recognize a malfunction and deal with it promptly if the operator has performed any unintended operation on the syringe, which therefore realizes safe operation of the syringe.